Touch-sensitive illumination

ABSTRACT

Illumination functionality is combined with a touch-sensing functionality. A first electrical conductor and a second electrical conductor are located on a substrate. A pressure-sensitive element ( 113 ) is connected across the conductors and a light-emitting device ( 114 ) is also connected between the conductors. A control circuit alternates between energizing the pressure-sensitive element with current flowing in a first direction and driving the light-emitting device with current flowing in an opposite direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. 62/637,524 filed Mar. 2,2018, which was granted a license to file outside of the United Stateson Mar. 6, 2018, and from GB 1804352.1 filed Mar. 19, 2018.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for providingillumination. The present invention also relates to a method ofcombining an illumination functionality with a touch sensingfunctionality.

It is known to provide illumination, in which illuminating devices areconnected between a pair of conductors to provide an illuminating strip.It is also known to provide control devices for controlling a degree ofillumination. Control devices of this type often make use of a componenthaving a variable resistance and touch sensitive devices are known thatpresent a resistance that varies with a degree of applied pressure.

A known problem with illumination devices configured to provideillumination over a distributed area is that difficulties may arise interms of identifying how to control the illumination devices. Inparticular, although the illumination devices may be distributed, thetendency is to provide a single point of contact for a control device.Thus, in many applications, specific devices must be added and, in someapplications, these may be considered aesthetically undesirable.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan apparatus for providing illumination, comprising: a substrate; afirst electrical conductor and a second electrical conductor supportedby said substrate; a pressure-sensitive element connected across saidfirst electrical conductor and said second electrical-conductor; alight-emitting device additionally connected between said firstelectrical conductor and said second electrical conductor; and a controlcircuit configured to: energize said pressure-sensitive element byapplying electricity to said pressure-sensitive element of a firstpolarity; and drive said light-emitting-device by applying electricityto said light-emitting device of a second polarity, wherein said secondpolarity is opposite to said first polarity.

In an embodiment, the pressure-sensitive element is a variable resistiveelement, which is substantially non-conductive without an application ofpressure.

According to a second aspect of the present invention, there is provideda method of combining an illumination functionality with a touch-sensingfunctionality, comprising the steps of: establishing a first electricalconductor and a second electrical conductor on a substrate; connecting apressure-sensitive element across said first electrical conductor andsaid second electrical conductor; connecting a light-emitting devicebetween said first electrical conductor and said second electricalconductor; and alternating, by means of a control-circuit, between:energizing said pressure-sensitive-element with current flowing in afirst direction; and driving said light-emitting device with currentflowing in an opposite direction.

Embodiments of the invention will be described, by way of example only,with reference to the accompanying drawings. The detailed embodimentsshow the best mode known to the inventor and provide support for theinvention as claimed. However, they are only exemplary and should not beused to interpret or limit the scope of the claims. Their purpose is toprovide a teaching to those skilled in the art.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows an apparatus for providing illumination;

FIG. 2 shows a schematic representation of a circuit identified in FIG.1;

FIG. 3 shows an alternative schematic representation;

FIG. 4 illustrates tracks printed on a substrate;

FIG. 5 shows an example of a control circuit of the type identified inFIG. 1;

FIG. 6 illustrates an alternative embodiment;

FIG. 7 illustrates timing diagrams; and

FIG. 8 illustrates a two-dimensional alternative embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1

An apparatus for providing illumination is illustrated in FIG. 1. Theapparatus includes a substrate 101 that may take the form of adielectric strip. A first electrical conductor 111 and a secondelectrical conductor 112 are supported on the substrate 101. Apressure-sensitive element 113 is connected across the first electricalconductor and the second electrical conductor. In addition, alight-emitting device 114 is also connected between the first electricalconductor and the second electrical conductor.

A control circuit 115 is configured to produce an alternating output, toenergize the pressure-sensitive element 113 by applying electricity tothe pressure-sensitive element of a first polarity. Thereafter, thecontrol circuit 115 drives the light-emitting device by applyingelectricity to the light-emitting device of a second polarity, whereinthe second polarity is opposite to the first polarity. Thus, in thisexample, the pressure-sensitive element 113 is receptive to theapplication of pressure, and the light-emitting device 114 emits lightwhen driven.

In the embodiment of FIG. 1, additional similar devices are connectedbetween the first electrical conductor 111 and the second electricalconductor 112. Thus, FIG. 1 shows additional devices 121 to 136. Any ofthese devices may take the form of a pressure-sensitive element or alight-emitting device. In an embodiment, pressure-sensitive elements andlight-emitting devices alternate but many other configurations arepossible. For example, a greater number of light-emitting devices may beincluded to increase illumination or a greater number of touch-sensitivedevices may be included to increase touch sensitivity.

FIG. 2

A schematic representation of the circuit on the substrate 101 is shownin FIG. 2. The pressure-sensitive element 113 and the light-emittingdevice 114 may be seen as forming a first cell, with a similar secondcell built from devices 121, 122, a third cell from devices 123, 124 anda fourth cell from devices 125, 126. Thus, each of these cells issubstantially similar.

In this embodiment, when the pressure-sensitive elements are beingenergized, a positive voltage is applied to the second electricalconductor 112. Under these conditions, the light-emitting devices,implemented as light-emitting diodes 114, 122, 124 and 126 are reversebiased and as such do not conduct. Consequently, only thepressure-sensitive elements 113, 121, 123 and 125 are energized and areresponsive to the application of pressure.

The application of a voltage to the first electrical conductor 111 or tothe second electrical conductor 112 alternates, such that a positivevoltage is then applied to the first electrical conductor 111. Underthese conditions, the light-emitting diodes are forward biased and assuch conduct electricity. With sufficient current, thelight-emitting-diodes emit light and present a relatively lowresistance. In an embodiment, the pressure-sensitive elements, such asthe first pressure-sensitive element 113, are variable resistiveelements and are substantially non-conductive without an application ofpressure. Thus, without an application of pressure, pressure-sensitiveelements are energized but current flow is minimal.

When pressure is applied to a pressure-sensitive element, such aselement 113, the pressure-sensitive element presents a low (conductive)resistance, resulting in current being allowed to flow. The controlcircuit 115 is configured to identify this current and thereby identifya touch. However, in an embodiment, the light-emitting devices present aresistance that is substantially lower than this conductive resistancewhen being driven by the control circuit.

FIG. 3

In an embodiment, the pressure-sensitive element may be a QTC detectorthat presents a resistance in the order of one thousand ohms when a fullforce is applied. Consequently, even when conducting, the conductivityis much lower than that of the light-emitting diodes, such that verylittle current flows through the sensors when the diodes are beingilluminated; the light emitting diodes are not shunted out of circuitwhen a force is applied to make one or more of the elements conductive.However, it is possible that other pressure-sensitive devices could beused that present a substantially lower resistance when force isapplied. Consequently, an alternative configuration is shown in FIG. 3.

In the schematic representation of FIG. 3, a first electrical conductor311 is substantially similar to the first electrical conductor 111 and asecond electrical conductor 312 is substantially similar to the secondelectrical conductor 112. A plurality of cells 313, 314, 315 and 316 areincluded, each comprising a light-emitting diode 319 that issubstantially similar to light-emitting-diode 114. Thus, when a positivevoltage is applied to the first electrical conductor 311, thelight-emitting diodes 319 are illuminated.

The first cell 313 includes a pressure-sensitive device 317, which againhas a conductance that increases with applied pressure. In thisembodiment, it is possible that the resistance of the pressure-sensitiveelement may reduce to an extent that it effectively shorts-out the lightemitting diodes when a positive voltage is applied to a first electricalconductor 311. In order to avoid this, the pressure-sensitive element317 is connected in series with a conventional diode 318. Thus,conventional diode 318 is configured such that it is only conductivewhen a positive voltage is applied to the second electrical conductor312.

FIG. 4

In an embodiment, silver tracks 401 are printed onto the substrate 101.In an alternative embodiment, the tracks may be printed in carbon. Afirst electrical track 411 is provided along with a second electricaltrack 412. Light emitting devices are bonded, using an adhesive orsolder, onto a first pad 413 and a second pad 414. A QTC force sensingelement contacts interdigitated electrodes 415. A conventional diode 318is similarly bonded onto a third pad 416 and a fourth pad 417.

FIG. 5

An example of a control circuit 115 is shown in FIG. 5. Amicrocontroller 501 receives power from a positive rail 502 and themicrocontroller is also connected to ground 503. To illuminate thelight-emitting devices, a positive voltage is applied to an output port504, with a similar port 505 connected to ground. A series resistor 506provides current limiting for the light emitting devices.

In its alternative mode of operation, a positive voltage is applied tooutput port 505, which in turn energizes the pressure sensitiveelements. When pressure is applied, current flows back to the first port504 which now presents a ground connection. A third port 507 of themicrocontroller 501 receives an indication of the voltage dropped acrossresistor 506 which is now providing a reference resistor forming part ofa voltage divider with one or more conducting pressure sensitiveelements.

FIG. 6

In an alternative embodiment, as illustrated in FIG. 6, the individuallight emitting devices of each cell (such as light emitting device 319are replaced with a primary light-emitting diode 601, a secondarylight-emitting diode 602 and a tertiary light-emitting diode 603 that,when driven, emit light of differing colors. In an embodiment, theprimary light-emitting diode 601 emits red light, the secondarylight-emitting diode 602 emits green light and the tertiarylight-emitting diode 603 emits blue light.

A second electrical conductor 604 provides a connection to the cathodeof each of the light emitting diodes 601 to 603, along with a connectionto a pressure-sensitive element 605. Three electrical conductors of thefirst type are provided, consisting of a primary conductor 606, asecondary conductor 607 and a tertiary conductor 608. The anode of theprimary light-emitting diode 601 is connected to the primary conductor606. Thus, when a positive voltage is applied to the primary conductor606, the primary light-emitting diode 601 is illuminated. Similarly, theanode of the secondary light-emitting diode 602 is connected to thesecondary conductor 607. Consequently, the secondary light-emittingdiode 602 (green) is illuminated when a positive voltage is applied tothe secondary conductor 607. The anode of the tertiary light-emittingdiode 603 (blue) is connected to the tertiary conductor 608.Consequently, when a positive voltage is applied to the tertiaryconductor 608 the third light-emitting diode 603 is illuminated.

When a positive voltage is applied to the second electrical conductor604, light emitting diodes 601 to 603 are reversed biased, therefore itis only possible for current to flow through the pressure-sensitiveelement 605, as previously described.

FIG. 7

Configurations described herein facilitate the deployment of a method ofcombining an illumination functionality with a touch sensingfunctionality. A first electrical conductor and a second electricalconductor are established on a substrate. A pressure-sensitive elementis connected across the first electrical connector and the secondelectrical conductor. Additionally, a light-emitting device is connectedbetween the first electrical conductor and the second electricalconductor. A control circuit then alternates between energizing thepressure-sensitive element with current flowing in a first direction anddriving the light-emitting devices with current flowing in the oppositedirection.

In an embodiment, sensing is performed periodically. In an example,switching occurs at ten hertz and the period 701 between samples istherefore one hundred milliseconds. However, in an embodiment, it isonly necessary for the microcontroller 501 to scan the force sensor fora period of several microseconds. Consequently, the remaining durationof period 701 is available to provide illumination. Consequently, atfull illumination, it is not possible for a human eye to detect thatpart of the illumination cycle is missing due to the pressure sensingoperations that are being performed when current is flowing in theopposite (non-illuminating) direction.

In an embodiment, it would be possible for the pressure detectionfunctionality of the illuminating device to be used to control anyactivity and need not necessarily be related to the illumination itself.However, in a deployment of the present invention, the pressuresensitivity is used to control the illumination of the device itself.Consequently, as illustrated at 702, the microcontroller 501 mayinitiate a process by energizing the pressure-sensitive elements, asindicated by negative pulses 703 and 704 but refrain from driving thelight-emitting device, such that the light-emitting devices do not emitany light (they are off) and therefore do not consume any power.Furthermore, given that the pressure-sensitive devices are highlynon-conductive before pressure is applied, monitoring is possible whileagain consuming very little power.

Upon pressure being applied, this will be sensed during one or more ofthe negative sampling periods such that, thereafter, the light-emittingdevices may be driven, resulting in the generation of light. In anembodiment, it is possible that, after activation, the light-emittingdevices enter a full light-emitting state, such that an illuminatingvoltage is presented throughout the full duration, except when thereverse scanning pulses 703, 704 are being deployed. The light-emittingdevices could also remain on until an external power supply is removed.

In an alternative embodiment, the light-emitting devices remain on untila second application of pressure is detected such that, in response tothis, the light-emitting devices are deactivated in a toggle-likefashion.

In a further alternative embodiment, a driving current is adjusted toincrease an illumination level in response to additional pressuredetection. Thus, in this way, it is possible for the driving current tobe modified by a process of pulse-width-modulation.

In this example, after pressure has been detected, a positive pulse 705is deployed during each period. Thereafter, in response to detecting afurther application of pressure, the width of the driving pulse isincreased from that shown at 705 to that shown at 706. Thus, in thisexample, two light levels are obtained but it should be appreciatedthat, in alternative embodiments, a greater number of increments may beprovided.

Again, it is possible that after a maximum intensity has been reached,as indicated by pulse 706, the device could remain illuminated or couldbe switched off in response to receiving a further pulse. However, in analternative embodiment, the driving current is adjusted to reduce theillumination level in response to additional pressure detection, afterthe illumination level has reached a maximum intensity. Thus, havingreached an intensity indicated by pulse 706, a further application ofpressure results in the driving current being reduced in length to thepulse shown at 705, whereafter a further application of pressureswitches the illumination devices off as indicated at 702.

In an embodiment, the control circuit is configured to drive thelight-emitting devices for a duration that is substantially longer thanthat during which the control-circuit energizes the pressure-sensitiveelements. In an embodiment, the control circuit energizes thepressure-sensitive elements for less than two-per-cent (2%) and possiblyless than one-per-cent (1%) of an operational period. Thepressure-sensitive elements may be energized a plurality of times duringa one-second interval and, in an embodiment of this type, thepressure-sensitive element is energized between eight and twelve timesper second.

FIG. 8

Strips of the type described with reference to FIG. 3 may be used toconstruct a two-dimensional array, of the type illustrated in FIG. 8.This in turn presents a plurality of array locations, including a firstarray location 801, a second array location 802, a third array location803 and a fourth array location 804. Thus, the example shown in FIG. 8represents a 2×2 subsection of a much larger array having substantiallymore array locations.

In the example of FIG. 8, there is provided a first vertical strip 811,a second vertical strip 812, a first horizontal strip 813 and a secondhorizontal strip 814. Each strip (811 to 814) includes a first conductor821, 823, 825, 827 respectively. Similarly, each strip (811 to 814)includes a second conductor 822, 824, 826, 828 respectively. A positivevoltage is applied to the first conductors in order to illuminate thelight-emitting devices. A positive voltage is supplied sequentially (ina time multiplexed fashion) to the second conductors 822, 824, 826, 828to sample a selected sensing device.

Each array location includes a first light-emitting diode (831, 833,835, 837) connected between respective first conductors (821, 823, 825,827) and second conductors (822, 824, 826, 828). Each array locationalso includes a second light-emitting diode 832, 834, 836, 838 connectedbetween respective horizontal first and second conductors.

Each array location is sensed sequentially. Thus, this process may beinitiated by sensing the first array location 801, such that theremaining array locations illuminate. The second vertical strip 812 andthe second horizontal strip 814 are not being sensed and are thereforeilluminated. A positive voltage is applied to first conductor 823resulting in the illumination of LED 833 and LED 837. A positive voltageis applied to first conductor 827 resulting in the illumination of LED836 and LED 838. However, a positive voltage is not applied to firstconductor 825 which is grounded.

Second conductor 826 provides an output signal. Instead of a positivevoltage being applied to first conductor 821, a positive voltage isapplied to the second conductor 822. This results in the energization ofthe first pressure-sensitive element 841 along with a series connectedsecond pressure-sensitive element 842. Thus, when pressure is applied atthe first array location 801, the first pressure-sensitive element 841and the second pressure-sensitive element 842 become conductive,resulting in current flowing out through the second conductor 826 of thefirst horizontal strip 813. A voltage is then deleted across a referenceresistor.

The invention claimed is:
 1. An apparatus for providing illumination,comprising: a substrate; a first electrical conductor and a secondelectrical conductor supported by said substrate; a pressure-sensitiveelement connected across said first electrical conductor and said secondelectrical conductor; a light-emitting device connected between saidfirst electrical conductor and said second electrical conductor; and acontrol circuit configured to alternate between: energizing saidpressure-sensitive element by applying electricity to saidpressure-sensitive element of a first polarity; and thereafter drivingsaid light-emitting device by applying electricity to saidlight-emitting device of a second-polarity, wherein said second polarityis opposite to said first polarity.
 2. The apparatus of claim 1,wherein: said pressure-sensitive element is a variable resistiveelement; and said pressure-sensitive element is substantiallynon-conductive without an application of pressure.
 3. The apparatus ofclaim 1, wherein: said pressure-sensitive element presents a conductiveresistance when pressure is applied; said control circuit identifiessaid conductive resistance to identify a touch when energizing thepressure sensitive element; and said light-emitting device presents aresistance substantially lower than said conductive resistance whenbeing driven by said control circuit.
 4. The apparatus of claim 1,wherein said light-emitting device is a light-emitting diode.
 5. Theapparatus of claim 4, including additional electrical conductors forsupplying additional driving electricity to a multi-coloredlight-emitting device.
 6. The apparatus of claim 1, wherein: saidpressure-sensitive element is connected in series with a diode; and saiddiode prevents current-flow through said pressure-sensitive element whenthe control circuit drives said light-emitting device.
 7. The apparatusof claim 1, wherein said control circuit is configured to drive saidlight-emitting device for a duration that is substantially longer thanthat during which said control circuit energizes said pressuresensitive-element.
 8. The apparatus of claim 7, wherein said controlcircuit energizes said pressure-sensitive element for less than two percent (2%) of an operational period.
 9. The apparatus of claim 7, whereinsaid pressure-sensitive element is energized a plurality of times duringa one-second interval.
 10. The apparatus of claim 9, wherein saidpressure-sensitive element is energized between eight and twelve timesper second.
 11. A method of combining an illumination functionality witha touch-sensing functionality, comprising the steps of: establishing afirst electrical conductor and a second electrical conductor on asubstrate; connecting a pressure-sensitive element across said firstelectrical conductor and said second electrical conductor; connecting alight-emitting device between said first electrical conductor and saidsecond electrical conductor; and alternating, by means of acontrol-circuit, between: energizing said pressure-sensitive elementwith current flowing in a first direction; and driving saidlight-emitting device with current flowing in a direction opposite tosaid first direction.
 12. The method of claim 11, wherein said drivingstep is performed in response to detecting pressure applied to saidpressure-sensitive element.
 13. The method of claim 11, wherein adriving current is adjusted to increase an illumination level inresponse to additional pressure detection.
 14. The method of claim 13,wherein said driving current is modified by a process of pulse widthmodulation.
 15. The method of claim 13, wherein said driving current isadjusted to reduce said illumination level in response to additionalpressure detection, after said illumination level has reached a maximumintensity.